The present invention relates generally to signal conversion, and more particularly to a signal conversion or translating circuit for image transmission or recording systems. The invention also relates to an image recording apparatus incorporating the signal conversion circuit for improving the reproduced image quality by increasing the discrete steps of gradation during conversion of the original analog value of image density into a digital value.
One prior art method for recording half-tone images involves varying the size of a dot in a recording medium or field for each elemental picture area as a function of its image density or black level. However, difficulties have been encountered in varying the dot size in as many gradation steps as desired because of the limited range of variations.
Another prior art method involves varying the number and location of a dot within a matrix of rows and columns as a function of the image density of the elemental picture area. However, this prior art requires the use of a storage system in which the image density of elemental area is stored until it is converted into the corresponding dot matrix, resulting in an increase in cost.
Furthermore, the prior art methods fail to provide reproduction of images which are satisfactory in terms of gradation and sharpness.